Oxygen ion-conducting dense ceramic

Abstract

Preparation, structure, and properties of mixed metal oxide compositions and their uses are described. Mixed metal oxide compositions of the invention have stratified crystalline structure identifiable by means of powder X-ray diffraction patterns. In the form of dense ceramic membranes, the present compositions demonstrate an ability to separate oxygen selectively from a gaseous mixture containing oxygen and one or more other volatile components by means of ionic conductivities.

That which is claimed is: 
     
       1. A crystalline mixed metal oxide composition represented by   D.sub.α E.sub.α+β O.sub.δ     where D comprises at least one metal selected from the group consisting of magnesium, calcium, strontium, and barium, E comprises at least one element selected from the group consisting of vanadium, chromium, manganese, iron, cobalt, and nickel, α is a number in a range from about 1 to about 4, β is a number in a range upward from 0.1 to about 20, such that     1.1<(α+β)/α≦6,     and δ is a number which renders the compound charge neutral, wherein the crystalline mixed metal oxide composition has an crystalline structure comprising layers having a perovskite structure held apart by bridging layers having a different structure identifiable by means of powder X-ray diffraction pattern analysis, the composition such that a dense ceramic membrane comprising the composition exhibits electron conductivity and oxygen ion conductivity, and ability to separate oxygen from a gaseous mixture containing oxygen and one or more other volatile components by means of the conductivities.   
     
     
       2. The composition according to claim 1 wherein the crystalline mixed metal oxide has a powder X-ray diffraction pattern as follows:   ______________________________________                                    
Principal XRD Lines                                                       
Interplanar        Assigned                                               
Spacing d, Å   Strength                                               
______________________________________                                    
9.52 ± .05      Weak                                                   
3.17 ± .05      Weak                                                   
2.77 ± .05      Medium-Strong                                          
2.76 ± .05      Medium-Strong                                          
2.73 ± .03      Very Strong                                            
2.08 ± .03      Weak-Medium                                            
1.96 ± .02      Medium                                                 
1.90 ± .02      Weak-Medium                                            
1.592 ± .009    Weak-Medium                                            
1.587 ± .009    Medium                                                 
1.566 ± .009    Weak.                                                  
______________________________________                                    
     
     
     
       3. A dense ceramic membrane permeable to oxygen comprising the crystalline mixed metal oxide composition according to claim 1. 
     
     
       4. A crystalline mixed metal oxide composition represented by   (D.sub.1-y M'.sub.y).sub.α E.sub.α+β O.sub.δ     where D is a metal selected from the group consisting of magnesium, calcium, strontium, and barium, M' comprises at least one other metal selected from the group consisting of magnesium, calcium, strontium, barium, yttrium, lanthanum, copper, zinc, silver, cadmium, gold, and mercury, with the proviso that D and M' are different metals, E is at least one element selected from the group consisting of vanadium, chromium, manganese, iron, cobalt, and nickel, y is a number in a range from about 0.01 to about 0.95, α is a number in a range from about 1 to about 4, β is a number in a range from 0.1 to about 20, such that     1.1<(α+β)/α≦6,     and δ is a number which renders the compound charge neutral, wherein the crystalline mixed metal oxide composition has a crystalline structure comprising layers having a perovskite structure held apart by bridging layers having a different structure identifiable by means of powder X-ray diffraction pattern analysis, the composition such that a dense ceramic membrane comprising the composition exhibits electron conductivity and oxygen ion conductivity, and ability to separate oxygen from a gaseous mixture containing oxygen and one or more other volatile components by means of the conductivities.   
     
     
       5. The mixed metal oxide composition according to claim 4, wherein y is a number in a range from 0.1 to about 0.5, and β is a number in a range from about 0.1 to about 6. 
     
     
       6. The composition according to claim 5 wherein the crystalline mixed metal oxide has a powder X-ray diffraction pattern as follows:   ______________________________________                                    
Principal XRD Lines                                                       
Interplanar        Assigned                                               
Spacing d, Å   Strength                                               
______________________________________                                    
9.52 ± .05      Weak                                                   
3.17 ± .05      Weak                                                   
2.77 ± .05      Medium-Strong                                          
2.76 ± .05      Medium-Strong                                          
2.73 ± .03      Very strong                                            
2.08 ± .03      Weak-Medium                                            
1.96 ± .02      Medium                                                 
1.90 ± .02      Weak-Medium                                            
1.592 ± .009    Weak-Medium                                            
1.587 ± .009    Medium                                                 
1.566 ± .009    Weak                                                   
______________________________________                                    
     
     
     
       7. A crystalline mixed metal oxide composition represented by   D.sub.α (E.sub.1-x G.sub.x).sub.α+β O.sub.δ     where D is a metal selected from the group consisting of magnesium, calcium, strontium, and barium, E is an element selected from the group consisting of vanadium, chromium, manganese, iron, cobalt, and nickel, G comprises at least one other element selected from the group consisting of vanadium, chromium, manganese, iron, cobalt, nickel, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, indium, tin, antimony, rhenium, lead, and bismuth, with the proviso that E and G are different elements, x is a number in a range from about 0.01 to about 0.95, α is a number in a range from about 1 to about 4, β is a number in a range from 0.1 to about 20, such that     1.1>(α+β)/α≦6,     and δ is a number which renders the compound charge neutral, wherein the crystalline mixed metal oxide composition has a crystalline structure comprising layers having a perovskite structure held apart by bridging layers having a different structure identifiable by means of powder X-ray diffraction pattern analysis, the composition such that a dense ceramic membrane comprising the composition exhibits electron conductivity and oxygen ion conductivity, and ability to separate oxygen from a gaseous mixture containing oxygen and one or more other volatile components by means of the conductivities.   
     
     
       8. A crystalline mixed metal oxide composition represented by   (D.sub.1-y M'.sub.y).sub.α (E.sub.1-x G.sub.x).sub.α+β O.sub.δ     where D is a metal selected from the group consisting of magnesium, calcium, strontium, and barium, M' is a metal selected from the group consisting of magnesium, calcium, strontium, barium, copper, zinc, silver, cadmium, gold, and mercury, E is an element selected from the group consisting of vanadium, chromium, manganese, iron, cobalt, and nickel, G is an element selected from the group consisting of vanadium, chromium, manganese, iron, cobalt, nickel, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, indium, tin, antimony, rhenium, lead, and bismuth, with the proviso that D, E, G and M' are different elements, y is a number in a range from about 0.1 to about 0.5, x is a number in a range from about 0.1 to about 0.8, α is a number in a range from about 1 to about 4, β is a number in a range from 0.1 to about 20, such that     1.1<(α+β)/α≦6,     and δ is a number which renders the compound charge neutral, wherein the crystalline mixed metal oxide composition has an crystalline structure comprising layers having a perovskite structure held apart by bridging layers having a different structure identifiable by means of powder X-ray diffraction pattern analysis, the composition such that a dense ceramic membrane comprising the composition exhibits electron conductivity and oxygen ion conductivity, and ability to separate oxygen from a gaseous mixture containing oxygen and one or more other volatile components by means of the conductivities.   
     
     
       9. The mixed metal oxide composition according to claim 8 wherein x is a number in a range from 0.1 to 0.8, and β is a number in a range from about 0.1 to about 6. 
     
     
       10. The mixed metal oxide composition according to claim 9 wherein D is strontium, E is iron, and G is cobalt. 
     
     
       11. The composition according to claim 10 wherein the crystalline mixed metal oxide has a powder X-ray diffraction pattern as follows:   ______________________________________                                    
Principal XRD Lines                                                       
Interplanar        Assigned                                               
Spacing d, Å   Strength                                               
______________________________________                                    
9.52 ± .05      Weak                                                   
3.17 ± .05      Weak                                                   
2.77 ± .05      Medium-Strong                                          
2.76 ± .05      Medium-Strong                                          
2.73 ± .03      Very Strong                                            
2.08 ± .03      Weak-Medium                                            
1.96 ± .02      Medium                                                 
1.90 ± .02      Weak-Medium                                            
1.592 ± .009    Weak-Medium                                            
1.587 ± .009    Medium                                                 
1.566 ± .009    Weak                                                   
______________________________________                                    
     
     
     
       12. A dense ceramic membrane permeable to oxygen comprising the crystalline mixed metal oxide composition. according to claim 10. 
     
     
       13. The mixed metal oxide composition according to claim 8 wherein x is a number in a range from 0.1 to 0.8, y is a number in a range from 0.1 to about 0.5, and β is a number in a range from about 0.1 to about 6. 
     
     
       14. The mixed metal oxide composition according to claim 13 wherein D is strontium, E is iron, and G is cobalt. 
     
     
       15. The composition according to claim 14 wherein the crystalline mixed metal oxide has a powder X-ray diffraction pattern as follows:   ______________________________________                                    
Principal XRD Lines                                                       
Interplanar        Assigned                                               
Spacing d, Å   Strength                                               
______________________________________                                    
9.52 ± .05      Weak                                                   
3.17 ± .05      Weak                                                   
2.77 ± .05      Medium-Strong                                          
2.76 ± .05      Medium-Strong                                          
2.73 ± .03      Very Strong                                            
2.08 ± .03      Weak-Medium                                            
1.96 ± .02      Medium                                                 
1.90 ± .02      Weak-Medium                                            
1.592 ± .009    Weak-Medium                                            
1.587 ± .009    Medium                                                 
1.566 ± .009    Weak                                                   
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       16. A dense ceramic membrane permeable to oxygen comprising the crystalline mixed metal oxide composition according to claim 14.